Disability rates are extremely high in older coronary patients. Determinants of disability were studied in 17 patients (12 men, 5 women), age 65-88 years (mean 73 +/- 7 years) with chronic coronary heart disease (CHD). All patients were at least 6 months after myocardial infarction (N=6), coronary revascularization (N=7), or had angina pectoris (N=4). Disability was measured from the physical function scale of the Medical Outcomes Study (MOS-SF36) questionnaire (scaled 0-100), applied to the home setting. Data collection included exercise testing with expired gas analysis, rest and exercise echocardiography, body composition analysis by dual x-ray absorptiometry, handgrip and leg extensor strength, a depression score and the MOS-SF36 health questionnaire. The best predictors of physical function score were peak aerobic capacity and depression score (r=.67 and .66 respectively, both P</= 0.005). Handgrip and leg extensor strength were also significant predictors (r=.54 and .46 respectively, both P</= 0.05). Measures of left ventricular systolic and diastolic function, body composition and exertional angina did not predict physical function score. The best predictors of peak aerobic capacity were exercise cardiac output )r=.64), exercise ejection fraction (r=.51), and lean body mass (r=.39, each P </= 0.05). There was a trend to lower physical function scores (62 +/- 22 vs 70 =/- 19) and lower aerobic capacity (14 +/- 6 vs 19 +/- 6 mls/kg/min) in women vs. men (both P </= 0.10). These data suggest that interventions aimed at increasing aerobic capacity and strength, and at decreasing mental depression would improve physical functioning in older CHD patients.